The U.S. Resource Conservation and Recovery Act (RCRA), the National Pollutant Discharge Elimination System (NPDES), and the National Emissions Standards for Hazardous Air Pollution regulations (NESHAP) strictly regulate the emission and discharge of volatile organic compounds (VOCs). Technical and regulatory difficulties associated with current VOC and hazardous air pollutant (HAP) treatment methods such as air-stripping (dilution), activated-carbon absorption, incineration, and thermal-catalytic treatment have prompted the search for alternatives. The drawbacks of present methods result in ineffective treatment, the generation of large secondary waste streams, and increased costs. It is also recognized that, for example, to operate fossil-fueled motor vehicles and other combustion-related engines or machinery under higher efficiency and reduced pollution output conditions in the future, it is desirable to have clean-burning, energy-efficient, hydrocarbon liquid fuels. This invention can also be used to synthesize such fuels from gaseous feedstocks.
The present invention has recognized these prior art drawbacks, and employs electrical discharges/non-thermal plasmas in a gaseous medium to destroy air pollutants or undesirable chemicals/chemical or biological agents; process chemicals, or synthesize chemical compounds. In non-thermal plasmas, the electrons are “hot”, while the ions and neutral species are “cold” which results in little waste enthalpy being deposited in a process gas stream. This is in contrast to thermal plasmas, where the electron, ion, and neutral-species energies are in thermal equilibrium (or “hot”) and considerable waste heat is deposited in the process gas.
The present invention improves formation of active species formed from the injection of additive gases/chemical compounds into a process gas stream to increase the efficiency and/or selectivity of the plasma processing by providing a shaped injection electrode that enhances and/or tailors the electric field near the additive-gas injection holes/ports.
Various objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.